This kind of vacuum vapor processing apparatus is used to improve the magnetic properties of, e.g., a Nd—Fe—B (or a Nd—Fe—B system) sintered magnet, and there is known one which is constituted by a hermetically sealed vessel made up of glass tube, and the like and an electric furnace. In this vacuum vapor processing apparatus, an object to be processed which is the Nd—Fe—B sintered magnet and a metal evaporating material which is rare earth metal selected from the group consisting of Yb, Eu, Sm are contained, in a mixed state, inside the hermetically sealed vessel. The pressure inside the vessel is reduced to a predetermined pressure by means of a vacuum pump or the like and sealed and, thereafter, the above materials are contained inside the electric furnace and are heated (e.g., to 500° C.) while this hermetically sealed vessel is rotated.
Once the hermetically sealed vessel is heated, the metal evaporating material evaporates to thereby form a metal vapor atmosphere inside the hermetically sealed vessel. The metal atoms in the metal vapor atmosphere get adhered to the sintered magnet that has been heated to substantially the same temperature. In addition, as a result of diffusion of the adhered metal atoms into the grain boundary phases of the sintered magnet, the metal atoms are homogeneously introduced in a desired amount into the surface of the sintered magnet and the grain boundary phases, whereby magnetization and coercive force are improved or recovered (patent document 1 and patent document 2).
Patent document 1: JP-A-2002-105503 (see, e.g., FIG. 1 and FIG. 2)
Patent document 2: JP-A-2004-296973 (see, e.g., claims)